<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            width: 200px;
            height: 200px;
            background-color: red;
            /* 模块隐藏 */
            /* display: none; */
            /* 模块透明 0-1；*/
            /* opacity: .5; */
            /* opacity: 0; */
            /* 模块不可见 */
            visibility: hidden;
        }

        .box p {
            /* opacity: 1; */
            /* display: block; */
            /* 模块可见 */
            visibility: visible;
        }
    </style>
</head>

<body>
    <div class="box">
        内容
        <p>OK</p>
    </div>
    <div>你好</div>
</body>

</html>